Clinical signs began on July 12, 15 and 18. All horses had no recent travel history, no or unknown vaccine history and all were euthanized for humane reasons. This is the third and fourth confirmed EEE cases in Osceola County, the first case in Highlands County and cases 14, 15 and 16 in Florida for 2016.

In Maryland, the Department of Agriculture (DOA) has reported two Potomac Horse Fever cases in Frederick County, in which one died.

The causative agent is the bacterium, Neorickettsia risticii.

Clinical signs include mild to severe fever, diarrhea, loss of appetite, laminitis, and mild colic. Potomac Horse Fever is most commonly contracted by horses that ingest infected aquatic insects such as caddisflies and mayflies.

“Potomac Horse Fever surfaces here every few years,” said State Veterinarian Michael Radebaugh. “Because it can be fatal, we urge horse owners to pay special attention to how their horses feel. The vaccine for Potomac Horse Fever is not always effective, so we encourage owners to contact their veterinarian sooner rather than later if they suspect anything, even if the horse has been vaccinated.”